Photoinitiators, also known as a photosensitizer or photocuring agent, is a kind of compounds absorbing certain wavelengths of energy in the range of the UV region (250˜420 nm) or visible light region (400˜800 nm) to generate free radicals or cations, causing monomers crosslinking. Radiation curing technology is a new energy-saving technology. Curing by ultraviolet (UV) and electron beam (EB), infrared light, visible light, laser, chemical fluorescence radiation, is in full compliance with “5E” Features: Efficient (efficiency), Enabling (utility), Economical (economy), Energy Saving (saving), Environmental Friendly (environmentally friendly), therefore is deemed as the “green technology”. Photoinitiator is one of the important components of a photo-curing adhesive, whose cure rate plays a decisive role. After the photo-initiator agent is irradiated by UV, it absorbs light energy and splits into two active free radicals, triggering photosensitive resin and reactive diluents chain polymerization, so that the adhesive crosslinks. It is rapid, environmental protection, energy saving.
In these days, the photoinitiators have been widely used in paintings, ink industry. With the improvement of people's living standards, the environment and food safety issues get more attention. Packaging industry, especially color printing in the food packaging industry, harmful volatile organic compounds (VOC), such as benzene, carbon tetrachloride, chloroform, etc., are now with clear limitations. Photoinitiators used for the food sector in the past, such as benzophenone, stilbene dione, which produce benzene during the use, have been banned from use in food-related printing industry. In addition, the present photoinitiators can not meet the requirements of the users because of their performance or price.
Therefore, in the photopolymerization technology field, it is still needed to have a photoinitiator with higher activity, readier to be prepared and handled. The present invention surprisingly found that, the new compounds 1-(4-tert-butyl-phenyl)-2-methyl-2-(1-piperidyl)-1-acetone and 1-(4-tert-butyl-phenyl)-2-methyl-2-(1-morpholinyl)-1-acetone are extremely effective photoinitiator, and in comparison with the existing photoinitiators, especially the widely used 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, production costs are significantly reduced, while the production process is much simpler, post-treatment is much simpler, therefore meet the environment protection requirements.